As a device separating particles having different specific gravities, there is mentioned a gravity separation device. As this gravity separation device, for example, a device in which a mixed material that is a target to be separated is supplied as slurry from an upper portion thereof, water is injected from the middle portion (incidentally, this water is referred to as “injected water”), and specific gravity separation of the slurry is performed by the upward flow of the injected water can be mentioned. Specifically, particles included in the mixed material are separated into the upper portion or a lower portion of the gravity separation device by a difference between the upward flow of the injected water and the precipitation rate of the precipitated particles.
As for separation control of the gravity separation device, a method of performing separation control by adjusting an opening degree of a bottom outlet valve with respect to a pressure meter provided on the wall surface of an upper portion of an addition line for injected water is general. Incidentally, as for the type of valves, a pinch valve or a butterfly valve is used.
However, in the inside of the gravity separation device, for example, shelving or flushing as shown in a dry hopper occurs, and it is difficult to supply, at a stable flow rate, an intermediate separated in the lower portion of the gravity separation device (hereinafter, referred to as “underflow”) to be provided to a subsequent treatment step. Further, in a case where the flow rate of the separated underflow exceeds a controllable range, a problem also arises in that the slurry of the underflow overflows from a receiving tank (intermediary tank) provided continuously to the gravity separation device.
Patent Document 1 discloses a technique of a hydrometallurgical process for recovering nickel from nickel oxide ore using a high pressure acid leaching method in which abrasion of facilities caused by ore slurry is suppressed, the amount of a final neutralization residue is reduced, and impurity components are separated and recovered for recycling.
Specifically, disclosed is a hydrometallurgical process for nickel oxide ore based on a high pressure acid leaching method, the process including at least one step selected from Step A: separating and recovering chromite particles in ore slurry by a recovery process including a specific gravity separation method; Step B-1: carrying out a leaching treatment on ore slurry that has a lowered Cr grade and carrying out a neutralization treatment using a Mg-based neutralizer such as Mg(OH)2 on a leachate obtained by solid-liquid separation; and Step B-2: carrying out a leaching treatment on ore slurry that has a lowered Cr grade and carrying out a neutralization treatment using a Mg-based neutralizer such as Mg(OH)2 on leaching residue slurry obtained by solid-liquid separation to recover hematite particles.
However, this Patent Document 1 does not disclose at all that a predetermined amount of a concentrate obtained by using a specific gravity separation method is stably supplied to a subsequent treatment step.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2005-350766